"""Custom-element builder, registry, and TypeScript codegen.

A custom element is a light-DOM Web Component: the Python builder emits a
semantic tag whose typed props become kebab-case attributes and whose behavior
lives in a compiled TS module (loaded via Media). One ``TypedDict`` per element
is the single source of truth for the server<->client contract;
``gen_element_types`` turns each registered spec into a TS interface + attribute
reader so drift fails ``tsc``.
"""

from dataclasses import dataclass
from typing import Mapping, TypedDict, get_type_hints

from common.components.core import Children, Element, HTMLAttribute, Media, Node


@dataclass(frozen=True)
class ElementSpec:
    tag: str  # e.g. "game-status-selector"
    ts_name: str  # e.g. "GameStatusSelector"
    props: type  # a TypedDict subclass


ELEMENT_REGISTRY: list[ElementSpec] = []


def register_element(tag: str, ts_name: str, props: type) -> None:
    """Register an element so codegen can emit its TS contract."""
    ELEMENT_REGISTRY.append(ElementSpec(tag, ts_name, props))


def _kebab(name: str) -> str:
    return name.replace("_", "-")


def custom_element(
    tag: str, props: Mapping[str, object], *, children: Children = None
) -> Node:
    """Emit ``<tag kebab-attrs>children</tag>`` and declare its compiled module.

    The module path mirrors the source layout: ``ts/elements/<tag>.ts`` compiles
    to ``dist/elements/<tag>.js``, which ``Media`` loads via ``ModuleScript``."""
    attributes: list[HTMLAttribute] = [
        (_kebab(key), value)  # type: ignore[misc]
        for key, value in props.items()
    ]
    return Element(tag, attributes, children).with_media(
        Media(js=(f"dist/elements/{tag}.js",))
    )


# ── Codegen ──────────────────────────────────────────────────────────────────

_TYPE_MAP = {int: "number", float: "number", str: "string", bool: "boolean"}


def _camel(name: str) -> str:
    head, *tail = name.split("_")
    return head + "".join(part.title() for part in tail)


def _reader_expr(name: str, python_type: type) -> str:
    attr = _kebab(name)
    if python_type in (int, float):
        return f'Number(el.getAttribute("{attr}"))'
    if python_type is bool:
        return f'el.getAttribute("{attr}") === "true"'
    return f'el.getAttribute("{attr}") ?? ""'


def _ts_for_spec(spec: ElementSpec) -> str:
    hints = get_type_hints(spec.props)
    interface_lines = "\n".join(
        f"  {_camel(name)}: {_TYPE_MAP[python_type]};"
        for name, python_type in hints.items()
    )
    reader_lines = "\n".join(
        f"    {_camel(name)}: {_reader_expr(name, python_type)},"
        for name, python_type in hints.items()
    )
    return (
        f"export interface {spec.ts_name}Props {{\n{interface_lines}\n}}\n\n"
        f"export function read{spec.ts_name}Props(el: HTMLElement): "
        f"{spec.ts_name}Props {{\n  return {{\n{reader_lines}\n  }};\n}}"
    )


def render_props_module() -> str:
    """The full ``ts/generated/props.ts`` content for every registered element."""
    header = "// GENERATED by `manage.py gen_element_types` — do not edit.\n"
    blocks = [_ts_for_spec(spec) for spec in ELEMENT_REGISTRY]
    return header + "\n" + "\n\n".join(blocks) + "\n"


# ── Element prop schemas (registered at import time) ─────────────────────────


class GameStatusSelectorProps(TypedDict):
    game_id: int
    status: str
    csrf: str


register_element("game-status-selector", "GameStatusSelector", GameStatusSelectorProps)